Signal detection using sphere decoding technique

Abstract

Method and apparatus for detecting a signal are disclosed, wherein first set of symbols represents a signal received in a receiver. A second set of symbols is estimated, representing the signal transmitted at a transmitter using a sphere decoding technique. The estimation may employ at least two modulation schemes. Reliability information relating to bits forming a symbol may be determined for at least one symbol of the second set. Furthermore, reliability information relating to the signal may be taken into account in estimating at least one symbol of the second set.

1. A method, comprising:
 receiving a first set of symbols representing a signal received in a receiver; and 
 estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein said estimating defines a vector and each vector value of the vector contains a modulation scheme, said estimating concurrently employing at least two modulation schemes. 
 
   
   
     2. The method as defined in  claim 1 , wherein said estimating the second set of symbols comprises adjusting a search volume of the sphere decoding technique based on said at least two modulation schemes. 
   
   
     3. The method as defined in  claim 1 , wherein said estimating the second set of symbols comprises determining a modulation scheme of a symbol of said second set of symbols. 
   
   
     4. The method as defined in  claim 3 , wherein said estimating the second set of symbols comprises defining a search region for said symbol of said second set of symbols using the modulation scheme of said symbol. 
   
   
     5. The method as defined in  claim 1 , wherein said estimating step comprises employing said at least two modulation schemes, in which said at least two modulation schemes comprise at least two different quadrature amplitude modulation schemes. 
   
   
     6. The method as defined in  claim 1 , wherein said estimating comprises employing said at least two modulation schemes, in which said at least two modulation schemes comprise at least two different phase shift keying modulation schemes. 
   
   
     7. The method as defined in  claim 1 , further comprising
 determining reliability information relating to bits forming a symbol for at least one symbol of said second set of symbols. 
 
   
   
     8. The method as defined in  claim 7 , further comprising taking reliability information relating to said signal into account in estimating at least one symbol of the second set of symbols. 
   
   
     9. The method as defined in  claim 1 , further comprising taking reliability information relating to said signal into account in estimating at least one symbol of the second set of symbols. 
   
   
     10. A method, comprising:
 receiving a first set of symbols representing a signal received at a receiver; 
 estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique; 
 determining a symbol constellation defining a relationship between a plurality of the second set of symbols and a plurality of bit sequences; 
 determining a first sub-constellation of the second set of symbols relating to a given bit of a bit sequence having a value of 1; 
 determining a second sub-constellation of the second set of symbols relating to a said given bit of a bit sequence having a value of 0; and 
 determining reliability information relating to bits forming a symbol for at least one symbol of said second set of symbols. 
 
   
   
     11. The method as defined in  claim 10 , wherein said estimating comprises estimating said second set of symbols step before said determining reliability information. 
   
   
     12. The method as defined in  claim 10 , further comprising determining the reliability information for at least a first symbol of said second set of symbols before estimating a second symbol of the second set of symbols. 
   
   
     13. The method as defined in  claim 12 , said estimating the second set of symbols step comprises using the reliability information relating to said first symbol of said second set of symbols in estimating said second symbol of said second set of symbols. 
   
   
     14. The method as defined in  claim 10 , further Comprising:
 determining a smallest first distance between a symbol of said first set of symbols and said first sub-constellation of symbols, and 
 determining a smallest second distance between said symbol of said first set of symbols and said second sub-constellation of symbols. 
 
   
   
     15. The method as defined in  claim 14 , wherein said determining the reliability information comprises using at least said smallest first distance and said second smallest distance for determining said reliability information. 
   
   
     16. The method as defined in  claim 10 , further comprising determining probability information per bit 
   
   
     17. The method as defined in  claim 16 , further comprising determining log-likelihood probabilities per bit 
   
   
     18. The method as defined in  claim 10 , wherein the determining comprises determining the reliability of information, in which reliability information relating to said signal is taken into account in estimating the at least one symbol of the second set of symbols. 
   
   
     19. A method, comprising:
 receiving a first set of symbols representing a signal received at a receiver; and 
 estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein reliability information relating to bits forming a symbol of the second set of symbols is taken into account in estimating at least one symbol of the second set of symbols, wherein 
 the reliability information defines a symbol constellation relationship between a plurality of the second set of symbols and a plurality of bit sequences, 
 a first sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 1, and 
 a second sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 0. 
 
   
   
     20. The method as defined in  claim 19  further comprising receiving said reliability information relating to said signal. 
   
   
     21. The method as defined in  claim 19 , further comprising
 determining the reliability information relating to said signal for a first symbol of said second set of symbols based on at least a second symbol of said second set of symbols. 
 
   
   
     22. The method as defined in  claim 19  wherein said estimating said second set of symbols comprises modifying candidate symbols based on at least said reliability information. 
   
   
     23. The method as defined in  claim 22  wherein said modifying the candidate symbols comprises modifying the candidate symbols that belong to a search region defined for estimating a symbol of said second set of symbols. 
   
   
     24. The method as defined in  claim 19 , wherein said estimating said second set of symbols step comprises modifying a symbol of said first set of symbols based on at least said reliability information. 
   
   
     25. The method as defined in  claim 24 , wherein said modifying comprises weighting. 
   
   
     26. The method as defined in  claim 19 , wherein said receiving reliability information comprising receiving said reliability information which comprises a priori bit probabilities. 
   
   
     27. The method as defined in  claim 19 , wherein said estimating said second set of symbols comprises determining bit probabilities for a symbol of said second set of symbols given a respective symbol of said first set of symbols. 
   
   
     28. The method as defined in  claim 19 , further comprising
 representing the first set of symbols using a linear transformation of the second set of symbols. 
 
   
   
     29. The method as defined in  claim 28 , wherein said representing said linear transformation step comprising relating to channels of a multiple-input-multiple-output system, in which each symbol of said second set of symbols represents a symbol transmitted by an antenna of the multiple-input-multiple-output system. 
   
   
     30. The method as defined in  claim 28 , wherein said representing said linear transformation step comprises relating to multiple paths in a time division system, in which said second set of symbols represents sequential symbols of a user of the time division system. 
   
   
     31. The method as defined in  claim 28 , wherein said representing said linear transformation step comprising relating to different codes of a code division system, in which each symbol of said second set of symbols relates to a different code. 
   
   
     32. A method, method, comprising:
 receiving a first set of symbols representing a signal received at a receiver; and 
 estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein reliability information relating to said signal is taken into account in estimating at least one symbol of the second set of symbols, wherein 
 said estimating said second set of symbols comprises determining averaged probabilities of a priori bit probabilities comprised in said reliability information and bit probabilities given symbols of said first set of symbols. 
 
   
   
     33. An apparatus, comprising:
 a receiver configured to receive a first set of symbols representing a signal received at a receiver antenna; and 
 an estimator configured to estimate a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein 
 said estimator is configured to define a vector and each vector value of the vector contains a modulation scheme, and to concurrently employ at least two modulation schemes in estimating said second set of symbols. 
 
   
   
     34. The apparatus as defined in  claim 33 , wherein the estimator is configured to determine reliability information relating to bits forming a symbol for at least one symbol of said second set of symbols. 
   
   
     35. The apparatus as defined in  claim 33 , wherein the estimator is configured to take into account reliability information relating to said signal in estimating at least one symbol of the second set. 
   
   
     36. The apparatus as defined in  claim 33 , wherein the estimator is configured to take into account reliability information relating to said signal in estimating at least one symbol of the second set. 
   
   
     37. The apparatus as defined in  claim 33 , further comprising a receiver block. 
   
   
     38. The apparatus as defined in  claim 33 , further comprising a communications device. 
   
   
     39. The apparatus as defined in  claim 33 , further comprising a network element for a communications system. 
   
   
     40. An apparatus, comprising:
 a receiver configured to receive a first set of symbols representing a signal received at a receiver antenna; 
 an estimator configured to estimate a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique; and 
 a determiner configured to
 determine a symbol constellation defining a relationship between a plurality of the second set of symbols and a plurality of bit sequences, 
 determine a first sub-constellation of the second set of symbols relating to a given bit of a bit sequence having a value of 1, 
 determine a second sub-constellation of the second set of symbols relating to said given bit of a bit sequence having a value of 0, and 
 determine reliability information relating to bits forming a symbol for at least one symbol of said second set of symbols. 
 
 
   
   
     41. The apparatus as defined in  claim 40 , wherein the estimator is configured to take into account reliability information relating to said signal in estimating the at least one symbol of the second set of symbols. 
   
   
     42. The apparatus as defined in  claim 40 , further comprising a receiver block. 
   
   
     43. The apparatus as defined in  claim 40 , further comprising a communications device. 
   
   
     44. The apparatus as defined in  claim 40 , further comprising a network element for a communications system. 
   
   
     45. An apparatus as defined in  claim 40 , further comprising a network element for a communication system, wherein said apparatus is configured to estimate a second set of symbols by determining averaged probabilities of a priori bit probabilities comprised in said reliability information and bit probabilities given symbols of said first set of symbols. 
   
   
     46. An apparatus, comprising:
 a receiver configured to receive a first set of symbols representing a signal received at a receiver antenna; and 
 an estimator configured to estimate a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein reliability information relating to the bits forming a symbol of the second set of symbols is taken into account in estimating at least one symbol of the second set of symbols, wherein 
 the reliability information defines a symbol constellation relationship between a plurality of the second set of symbols and a plurality of bit sequences, 
 a first sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 1, and 
 a second sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 0. 
 
   
   
     47. The apparatus as defined in  claim 46 , further comprising a receiver block. 
   
   
     48. The apparatus as defined in  claim 46 , further comprising a communications device. 
   
   
     49. The apparatus as defined in  claim 46 , further comprising a network element for a communications system. 
   
   
     50. A system, comprising:
 a receiver configured to receive a first set of symbols representing a signal received at a receiver antenna; and 
 an estimator configured to estimate estimating means for estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein 
 the estimator is configured to define a vector and each vector value of the vector contains a modulation scheme, and to concurrently employs at least two modulation schemes. 
 
   
   
     51. A system, comprising:
 receiver configured to receive a first set of symbols representing a signal received at a receiver antenna; 
 an estimator configured to estimate a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique; and 
 a determiner configured to
 determine a symbol constellation defining a relationship between a plurality of the second set of symbols and a plurality of bit sequences, 
 determine a first sub-constellation of the second set of symbols relating to a given bit of a bit sequence having a value of 1, 
 determine a second sub-constellation of the second set of symbols relating to said given bit of a bit sequence having a value of 0, and 
 determine reliability information relating to bits forming a symbol for at least one symbol of said second set of symbols. 
 
 
   
   
     52. A system, comprising:
 a receiver configured to receive a first set of symbols representing a signal received at a receiver antenna; and 
 an estimator configured to estimate a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein reliability information relating to the bits forming a symbol of the second set of symbols is taken into account in estimating at least one symbol of the second set of symbols, wherein 
 the reliability information defines a symbol constellation relationship between a plurality of the second set of symbols and a plurality of bit sequences, 
 a first sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 1, and 
 a second sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 0. 
 
   
   
     53. An apparatus, comprising:
 receiving means for receiving a first set of symbols representing a signal received at a receiver antenna; and 
 estimating means for estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein 
 said apparatus is configured to define a vector and each vector value of the vector contains a modulation scheme, and to concurrently employ at least two modulation schemes in estimating said second set of symbols. 
 
   
   
     54. An apparatus, comprising:
 receiving means for receiving a first set of symbols representing a signal received at a receiver antenna; 
 estimating means for estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique; and 
 determining means for determining constellation defining a relationship between a plurality of the second set of symbols and a plurality of bit sequences, determining a first sub-constellation of the second set of symbols relating to a given bit of a bit sequence having a value of 1, determining a second sub-constellation of the second set of symbols relating to said given bit of a bit sequence having a value of 0, and determining reliability information relating to bits forming a symbol for at least one symbol of said second set of symbols. 
 
   
   
     55. An apparatus, comprising:
 receiving means for receiving a first set of symbols representing a signal received at a receiver antenna; and 
 estimating means for estimating a second set of symbols representing said signal transmitted at a transmitter using a sphere decoding technique, wherein 
 reliability information relating to the bits forming a symbol of the second set of symbols is taken into account in estimating at least one symbol of the second set of symbols, 
 the reliability information defines a symbol constellation relationship between a plurality of the second set of symbols and a plurality of bit sequences, 
 a first sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 1, and 
 a second sub-constellation of the second set of symbols relates to a given bit of the bit sequence having a value of 0.